Automated pneumatic clamping devices are commonly utilized in manufacturing environments to secure a workpiece, such as a sheet metal part, to a base for processing, such as welding, punching, or assembly with other parts. Generally, conventional clamping devices comprise a piston and cylinder, wherein the piston is operable to translate within the cylinder in order to force a clamping member to rotate about an axis. FIG. 1 illustrates an exemplary prior art clamping mechanism 10 comprising a clamping member 12 which is rotatably coupled to a housing 14 via a fixed pivot pin 16. The clamping mechanism 10 is operable to generally clamp a flat part 18 between an end 20 of the clamping member 12 and the housing 14 by the application of air pressure to a cylinder 22. The application of air pressure to the cylinder 22 generally causes a piston 24 to translate therein, wherein a drive pin 26 associated therewith is operable to generally rotate the clamping member 12 about a single axis 28 associated with the fixed pivot pin 16.
Typically, the clamping member 12 is considered a wearable part, wherein the clamping member is replaced regularly. The clamping member 12 of the prior art, however, has typically been fairly difficult to remove from the housing 14, because a removal of several other components associated with the clamping member is typically required prior to the removal of the clamping member. Conventionally, the fixed pivot pin 16 is generally fixed to the housing 14 and the clamping member 12 is generally coupled to the pivot pin 16 via a hole 30 in the clamping member. Such a pin and hole arrangement, therefore, typically requires the pivot pin 16 to be removed from the housing 14 in order to remove and replace the clamping member 12. Furthermore, other components such as a location pin 32, and/or other components are also typically removed prior to the removal of the clamping member 12 from the housing 14. Removal of such components can increase maintenance time and cost associated with the prior art clamping mechanism 10.
Furthermore, many applications exist wherein the workpiece 18 comprises an upward-facing flange 34, and wherein a locking arm 36 associated with the clamping member 12 must clear the flange, yet still provide an adequate clamping force to the workpiece. The presence of the flange 34 can cause difficulties when dealing with conventional clamping mechanisms, since the conventional clamping mechanisms are generally limited to the fixed axis 28 of rotation of the clamping member 12.
Still further, typical pneumatic clamping devices of the prior art operate via a gas pressure (e.g., 60 PSI or greater) being applied to a first portion 38 or a second portion 40 of the cylinder 22 via a respective first port 42 or second port 44 which is in fluid communication with the cylinder. The piston 24 is generally forced by the gas pressure between a first position 46 and a second position 48 within the cylinder 22, depending on which of the first port 42 or the second port 44 is pressurized. Gas which resides in the second portion 38 of the cylinder 22, for example, is generally exhausted to atmosphere via the second port 44 upon an application of the gas pressure to the first port 42, thus causing the piston 24 to translate from the first position 46 to the second position 48. In general, a velocity of the piston 24 translating within the cylinder 22 rapidly accelerates upon the application of gas pressure to either of the first port 42 or the second port 44, and rapidly decelerates once the piston has reached an end 50 of the cylinder.
The travel seen by the piston 24 between the ends 50 of the cylinder 22 generally defines a stroke S of the piston. Typically, the rapid deceleration at the end of the stroke S of the piston 24 can produce unwanted impact forces, both to components of the pneumatic device 10 such as the piston 24, cylinder 22, drive pin 26, and clamping member 12, as well as undesirable forces exerted on the workpiece 18, wherein undesirable effects such as deformations or dimples may result in the workpiece. Conventional attempts to minimize the impact forces at the ends of the stroke S have included, for example, cushioning devices, such as a “snubber”. A typical snubber 52 illustrated in FIG. 1 comprises an additional self-contained snubber piston 54 and snubber cylinder 56, wherein a translational velocity of the snubber piston is generally limited by a gas or spring 58 residing within the snubber cylinder. Typically, the snubber 52 is arranged within the pneumatic device 10 such that the piston 24 of the pneumatic device contacts the snubber piston 56 near the end 50 of the stroke S of the pneumatic device, wherein the translation of the snubber piston generally slows the translation of the pneumatic device piston. Conventional cushioning devices for limiting impact forces, however, are generally prone to wear, and furthermore add complexity to the pneumatic device.
Therefore, a need exists for a clamping fixture which provides for easy removal of the clamping member from the fixture, as well as a need for a simple apparatus for minimizing impact forces seen in pneumatic devices.